FLOOD10502 ‎(2)‎

• County: Statewide
• Basin: Statewide
• Title: State of Colorado - 2007 Flood Documentation Reports
• Date: 8/1/2007
• Prepared For: CWCB
• Prepared By: ICON Engineering
• Floodplain - Doc Type: Floodplain Report/Masterplan

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located on-stream of Goldsmith Gulch, (George Wallace Park Detention Pond and the
Bible Park Detention Pond) and a third regional facility functions as an overflow, off-
channel detention (Iliff Pond). The George Wallace Park Pond is also known as the
Temple Pond detention and is located just upstream ofthe 1-225 crossing of Goldsmith
Gulch. The Bible Park detention is located upstream of Yale Avenue, and the Iliff Pond
is located downstream of Bible Park. Both the Temple Pond and the Iliff Pond facilities
have monitoring stations as a part of the Urban Drainage & Flood Control District's
ALERT system.

On May 14th, at approximately 19:51 hours, the Goldsmith Gulch ALERT Water Level
recorder at Temple Pond in George Wallace Park, had a recorded maximum flow of291
cfs, and the ALERT station at the Iliff Pond recorded a high flow of 425 cfs at 20:27
hours.

ICON conducted a field visit on the morning after the reported near drowning. A paved
trail system crosses Goldsmith Gulch about 1,000 feet upstream of Yale Avenue. The
trail crossing has a low flow opening that is 15-feet wide by 2.5-feet high. The concrete
trail is approximately 20-feet wide at the gulch crossing with a drop-off to the gulch
thalweg ofless than 3D-inches. The crossing does not have handrails. When flow levels
exceed the low flow capacity of the crossing, the concrete trail functions as a weir. High
water marks were noted as having overtopped the crossing, with a field measured
top width of 160- feet. The maximum depth of flow over the trail was 1.06- feet. Using a
combination of culvert flow and weir flow, we estimated the peak flow have been
approximately 468 cfs. This flow estimate confirms the ALERT flows.

Based on a review of available data from the ALERT sites, the resulting flows from the
May 14th rainfall are not particularly noteworthy from a frequency standpoint, and had, in
fact, been exceeded at least three previous times during 2007.

ICON Engineering, Inc

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